Keeper of the Lost Cities

The series tells the story of Sophie Foster, an elfish twelve-year-old high school senior with telepathy, the ability to control many aspects of the mind. She lives in San Diego, California with her human family.

She is on a school field trip, until another elfish teenager, Fitzroy Avery Vacker, tracks her down. He discusses the reality of their world with Sophie, and that she must move to the Lost Cities, a hidden place where elves, trolls, ogres, gnomes and dwarves live in harmony. She is forced to leave her human family behind and stay with an elvin couple, Grady and Edaline Ruewen, who later adopt her. She starts school at an elvin academy named Foxfire.

The main conflict in the series is between the Black Swan, a rebel organization, and the Neverseen, a group of criminal extremists. Sophie learns that the Black Swan are her creators. She learns that her old neighbor, from the human world, Mr. Forkle, is the director of the Black Swan's Project Moonlark, the project in which she was created. The Neverseen are a group of criminal extremists who believe that the Lost Cities, the home of the elves, are in dire need of major leadership and political changes. One of the goals of the Neverseen is to overthrow the Council, the leaders of the Lost Cities.

On January 11, 2021, it was announced that Ben Affleck would be directing an adaptation of Keeper of the Lost Cities for Walt Disney Pictures. The release date and cast have not been announced.[3][4] No new information has been released as of September 21, 2023.

• Sophie Elizabeth Foster: The main protagonist of the series. She is a Telepath, Inflictor, Polyglot, Teleporter, and Enhancer. Her genes, sourced from Councillor Oralie and an unknown elf, were tweaked by a rebel group called the Black Swan, giving her powerful elvin abilities. One of her parents is later revealed to be the Councilor Oralie in Legacy, but no one knows who his father is, just that it is not Kenric Fathdon or Councilor Bronte. She was raised by humans after her experimentation and brought back to the Lost Cities at age twelve to complete her education at the Foxfire Academy in addition to being adopted by Grady and Edaline Ruewen.
• Keefe Sencen: Sophie's close friend and soulmate, who is an Empath, allowing him to detect others' feelings. Unlike other Empaths, he is able to sense emotions without physical contact. In Unlocked, he also becomes a Polyglot, capable of speaking all languages, and manifests an unnamed ability of emotional manipulation along with an unnamed ability allowing him to sense and trigger abilities. He is also the cause of "The Great Gulon Incident."
• Fitzroy "Fitz" Avery Vacker: Sophie's close friend and first love. He is a highly skilled Telepath and becomes Sophie's Cognate, making them a close telepathic pair. After he and Sophie broke up, their Cognate relationship was damaged. He belongs to a prominent family of Elvin nobility. He is sometimes known for his temper issues, relying on anger when he is not sure how to feel, almost murdering his brother Alvar at one point in time.
• Dexter "Dex" Alvin Dizznee: Sophie’s best friend and a talented alchemist with Technopathy, the ability to manipulate technology, and her first kiss. He only appeared on one cover because of the choices he was forced to make by the council, like the Ability Restrictor in Everblaze, and the tracking device he made for Alvar in Flashback.
• Biana Amberly Vacker: Sophie’s enemy turned friend and Fitz’s younger sister. She is a Vanisher, allowing her to turn invisible. She is often found sneaking around and listening in on people's conversations. She has shown to be a popular character in Keeper of the Lost Cities, yet slowly loses friends after many of her family's secrets get revealed in the later books. She is an expert on fashion, and can look good when no one else can.
• Tam Dai Tong "Song": Sophie’s friend from Exilium, a school for banished and or "unruly" elves, who is a Shade, capable of manipulating shadows. Because of his status as a shade, he is rarely trusted by strangers. In Flashback, he is shown to be able to manipulate an element called "Shadowflux," showing to be very powerful through the later books.
• Linh Hai Tong "Song": Tam’s twin sister, also previously a student (a "Wayward") at Exilium, with Hydrokinesis, the ability to control water. She is known as “the girl of many floods” due to that fact that she caused many floods while mastering her Hydrokinesis, causing her to be banished from the Lost Cities. She later saves the city of Atlantis along with Sophie and Keefe, and holds the dome until Psionipaths show up, to reinforce and rebuild it.
• Marella Adene Redek: Sophie's gossipy friend with a rare and illegal special ability, pyrokinesis, letting her summon fire and bend it to her will. She has also recently been mentored by Fintan in the ability.
• Wylie Zoran Endal: The son of Prentice Endal, a key member of the Black Swan. He is a Flasher, which means he can sense and manipulate colors of light. He also lived with his adoptive father Tiergan after his father's memory break.
• Mr. Forkle: He is the leader of the Black Swan, along with the rest of the collective, and a fatherly parental figure to Sophie. When she was small, and still in the human world, he consumed ruckleberries, giving him a bloated look that reeked of feet. He signs his name as Errol Loki Forkle, or the acronym E.L.F. Secretly, he is two people. They were twins, but their parents were ashamed of having more than one child; an unusual occurrence in the elvin world. As a result, they shared memories and identities. Sadly, one of the Forkles died, after being stabbed by Gethen, a Telepath in the Neverseen. Since his later revelation, Sophie has learned the truth about his twin identity.
• Grady Howell Ruewen: He is Sophie's adoptive father, and is Edaline Ruewen's spouse. He is a Mesmer, and is part of the Nobility and works as an Emissary.
• Edaline Kelia Ruewen: She is Sophie's adoptive mother, and is Grady's spouse. She is a Conjurer, and rehabilitates animals with Grady.
• Councillor Oralie: Sophie's biological mother, an Empath, and has taken part in Project Moonlark.
• Councillor Bronte: Besides being known to have a cold attitude, he is one of the Lost Cities' only Inflictors (besides Sophie) and is part of the Council. He is currently the oldest member of the Council.
• Lady Gisela Minette Sencen: Keefe's mother, and the former leader of the Neverseen. She is a Polyglot and she hid the fact that she is a Conjurer for many years.